This invention relates generally to pump mechanisms and particularly to a pump mechanism for delivering ink or similar writing fluid from a reservoir to a writing device. The pump mechanism includes a piston slidably carried within a cylinder for reciprocatory movement to alternately draw ink from the reservoir into the cylinder and then to discharge the ink from the cylinder to the writing device.
In known pumping mechanisms of this general type and for this general purpose, a control mechanism such as a photo cell is provided to deenergize the pump when the ink in the reservoir is almost exhausted, thereby preventing entry of air bubbles into the inking system. Then, for drawing fresh ink into the inking system after the reservoir has been filled, manual suction and pressure pumps are provided.
These control mechanisms and manually operated pumps are complicated in design, expensive to manufacture and space consuming. In addition, the operation of the manual pumps is difficult and the entire pump mechanism is inoperative if air has become entrained therein.